Candles and some liquor bottles formed a small shrine near the shooting scene on Sixth Street Wednesday July 23, 2014. Two men were killed Tuesday near the corner of Sixth and Mission Streets in San Francisco, Calif. Marc-Anthony Salumbides and Daniel Beltran were killed near the Henry Hotel.

Two women who knew one of the victims very well stood by a small shrine on Sixth Street Wednesday July 23, 2014. Two men were killed Tuesday near the corner of Sixth and Mission Streets in San Francisco, Calif. Marc-Anthony Salumbides and Daniel Beltran were killed near the Henry Hotel.

On Sixth Street, friends and acquaintances stopped to pay their respects Wednesday July 23, 2014. Two men were killed Tuesday near the corner of Sixth and Mission Streets in San Francisco, Calif. Marc-Anthony Salumbides and Daniel Beltran were killed near the Henry Hotel.

Witnesses to one of the shootings said a bloody hand print is still evident on the street Wednesday July 23, 2014. Two men were killed Tuesday near the corner of Sixth and Mission Streets in San Francisco, Calif. Marc-Anthony Salumbides and Daniel Beltran were killed near the Henry Hotel.

After a relatively quiet first half of the year, San Francisco police on Wednesday were working to solve two gun killings that happened in an 18-hour span on the same gritty block of Sixth Street.

Daniel Beltran, 18, was shot after getting into a fight with two others in the lobby of the residential Henry Hotel at 106 Sixth St. near Mission Street at about 5 a.m. Tuesday, police said.

A day later, his friends said Beltran and another friend had gone into the hotel to buy marijuana, but had knocked on the wrong door.

"When you make a mistake on Sixth Street, you die," said one of Beltran's friends, who asked not to be identified. "He was just an average kid who lived in the neighborhood. He wasn't into gangs or anything."

Then, just after 11 p.m. Tuesday, 25-year-old Marc-Anthony Salumbides of Pacifica was gunned down feet from the Henry Hotel's entrance after another altercation.

His friends gathered Wednesday at a makeshift memorial around his bloody handprint, but declined to comment.

Police officials said Beltran and Salumbides knew each other. But investigators do not believe the Sixth Street killings were connected, said Police Chief Greg Suhr.

"It was an unfortunate coincidence that they happened within 100 yards of each other, but at this point in time, they do not seem to be related," Suhr said.

He said two suspects in Beltran's killing, who were apprehended Tuesday night, do not appear to have a relationship with a suspect in the later slaying.

The suspects in custody are Darius York, 34, and Joseph Young, 33, both of Fremont, who were arrested in Fremont and booked into county jail Wednesday morning on suspicion of murder.

The Sixth Street homicides extended a spate of violence in the city that has left six others dead this month. From January to June, the city tallied only 14 homicides and was on pace to record the lowest number of killings in San Francisco since 1954.

Chief Suhr said his officers were doing everything possible to stem the violence, particularly by focusing on taking illegal guns off the street and preventing shootings.

"We treat every shooting like an intended homicide," he said. "Very sadly, more shootings have resulted in homicides in June and July than did in January to May. On the high side, we have a lot of those responsible in custody."

Two San Francisco brothers, Kenyon Norbert, 22, and Kishawn Norbert, 21, were arrested on suspicion of killing two men in separate shootings in Visitacion Valley and the Bayview this month.

Lisa Heng, 30, was charged Monday with stabbing and murdering 40-year-old Matt Sheahan three days earlier in a hotel on the 1000 block of Geary Street.

"We're sending a message that you can't get away with murder in San Francisco," Suhr said. "We want that message to be really clear."